1. Field of the Invention
Present invention relates to a device and method for treating venous disorders in general, and more particularly, an endovascular radiation therapy device with catheter to prevent damages in vascular wall.
2. Invention Disclosure Statement
Endovascular laser therapy is an effective and minimally invasive way to close diseased or abnormal blood vessels, and can be an effective alternative to more invasive treatments such as vein stripping, or chemical treatments. It can be effectively applied to treat various vascular abnormalities and diseases such as varicose veins.
Generally, endovascular laser therapy is accomplished by inserting a flexible optical fiber into a blood vessel and advancing it until the distal end (emission end) of the fiber is located near the area of the blood vessel that is to be closed. Typically, an introducer catheter/sheath is first inserted and advanced to a position near the desired location to be irradiated. This allows the optical fiber to be advanced into position while avoiding possible damage to the blood vessel or fiber during advancement.
Before irradiation, the optical fiber is positioned so that the distal end of the fiber is located in the introducer sheath at some short distance from the distal end of the sheath. The sheath is then partially withdrawn or the fiber is advanced to expose the fiber's distal end within the blood vessel. A radiation source such as a laser is then activated, and radiation is transmitted to the distal end of the fiber and is applied to the vessel wall. Generally, in order to close a desired length of the blood vessel, the optical fiber and sheath are slowly withdrawn while radiation is applied to the blood vessel.
Present methods and equipment for vein closing attempt to bring the vein walls into contact with the fiber optic device used. For example, in U.S. Pat. No. 6,398,777 by Navarro, a method for treating blood vessels using endovascular techniques to deliver laser energy is disclosed. Laser energy of 532 and 1064 nm is delivered into the vein using fiber optics and angiocatheter. Vein closing is achieved by contact of fiber with blood vessel wall. Such contact can result in vessel wall perforation.
Other state of the art treatments may allow for accidental contact between the fiber's distal end and the vessel wall. This can pose the risk of perforations if certain energy levels are exceeded or other unfortunate circumstances arise. Perforations result in bleeding into the surrounding tissue, causing post-treatment bruising and its associated discomfort.
There are numerous attempts to avoid contact with the vessel wall and regulate irradiation during intravascular laser treatments.
A balloon would be a prior art way to do this, but balloons are complex, prone to complication, and affect the amount of radiation incident on vessel wall. Also, a balloon may interfere with vein closure.
U.S. Pat. No. 5,167,686 by Wong discloses a catheter for delivering ablative radiant energy to a blood vessel to remove obstructive biological material. Radiation is applied in such a way that the energy density of the emitted beam drops sharply so that material beyond the working zone is not removed. This helps to avoid the risk of puncturing the blood vessel, as material is removed in limited layers. A fiber optic waveguide is extended through the lumen of the catheter, terminates in the catheter and is secured with an optical system located at the distal end of the catheter. The optical system both protects the optic fiber and shapes the beam to achieve the limited ablation desired.
U.S. Application No. 2007179486A1 by Welch et al. discloses a laser fiber optic for endovascular laser therapy; having a heat resistant insulated tip shield, covering the distal end of optic fiber. The insulative tip shield has echogenic qualities to increase ultrasound reflectivity. The distal tip of the optical fiber of ½ to 2 cm is not covered by protective shield. The chance of exposed tip getting carbonized when in contact with blood cells can cause thermal destruction to tissue, reduced output and also can damage the fiber tip.
U.S. Pat. Nos. 7,273,478 and 7,559,329 by Appling disclose an endovascular treatment device for use with an optical fiber, featuring a spacer to position the distal end of the fiber away from the inner wall of the blood vessel to evenly distribute radiation to avoid perforation or uneven closure. The spacer is initially in an “undeployed state” during insertion, and a “deployed state” where it positions the optical fiber for irradiation. The spacer may include a plurality of ribs which radially expand to position the fiber. The spacer may be incorporated into a catheter or attached to the optical fiber.
US Application 2008/0021527 A1 by Hennings et al. provides an apparatus and method for treatment of varicose veins. The improved method used reduces the amount of heat, induces coagulum at the fiber tip and prevents heat damage. This invention uses infrared radiation in the range of 1.2-2.7 μm to irradiate endothelial cells and collagen of the vein wall thus permanently occluding the vessel. A non-hemoglobin absorbing wavelength e.g. 1320 nm with higher energy per pulse is used to avoid formation on coagulum at the fiber tip. It also proposes the use of a silica clad fiber and a spacer to prevent coagulum at the fiber tip. Disadvantages to this invention include the need of movable means to center the fiber, which may cause improper position if the spacer does not deploy properly. Also, because the spacer is in contact with the vessel wall, it may become damaged or deformed while the fiber and spacer are withdrawn during irradiation.
It is an object of the present invention to provide a simplified device for endovascular radiation treatments that avoids puncturing the vessel wall by preventing contact between the emission means of an optical fiber and the vessel wall. The present invention addresses this need.